"J-mats" or "Jack-off materials" refers to media that is worthy of masturbation. Common misconceptions include films such as Cruel Intentions and Into the Blue. Sex is indeed present in these films, however duration and graphic content do not provide enough time or desire to beat one out. Often times, one is left with a hard-on and the need to find real J-mats to finish the task. Any movie Jessica Alba partakes in falls into this dreadful fallacy. True thespians that indulge in J-mat media include Angelina Jolie, Shannon Tweed, Sharon Stone, and Anna Paquin (see metacafe.com for examples).
"Have you seen Diane Lane in Unfaithful? Pretty good J-mats..."
"Angelina Jolie has fallen off. She needs to make more j-mats."
"Amanda Seyfried's new movie looks like it might have some j-mats"